Conventionally, PTT calls are a form of calling.
In a PTT call, a given mobile communication terminal belonging to a group among a plurality of mobile communication terminals is granted speaking rights by a server managing the PTT call, and audio based on an audio signal from the given mobile communication terminal is output to the other mobile communication terminals in the group (e.g., see Patent Literature 1 and 2). In the PTT call, when a plurality of the mobile communication terminals make a request for speaking rights, the server grants the speaking rights to one of the mobile communication terminals among the requesting terminals having the highest priority rank for assigning the speaking rights.